The present invention relates to an epoxy resin composition for encapsulation of semiconductors and a semiconductor apparatus.
In accordance with the recent trend of market for miniaturization, weight-saving and high performance of electronic devices, high integration of semiconductors has advanced year by year, and, furthermore, surface mounting of semiconductor apparatus has been promoted. Under the circumstances, area mounting type semiconductor apparatuses have been newly developed and shifting to such new semiconductor apparatuses from those of conventional structures has started.
As area mounting type semiconductor apparatuses, representative are ball grid array (hereinafter referred to as “BGA”), and further miniaturized chip size package (hereinafter referred to as “CSP”), and these have been developed for meeting the demand for increase of the number of pins and speeding-up which have reached the limits with the surface mounting type semiconductor devices such as quad flat package (hereinafter referred to as “QFP”) and small outline package (hereinafter referred to as “SOP”).
As for the structures of the area mounting type semiconductor devices, semiconductor elements are mounted on one side of a rigid circuit substrate such as a bismaleimide triazine (hereinafter referred to as “BT”) resin/copper foil circuit substrate or a flexible circuit substrate such as polyimide resin film/copper foil circuit substrate, and only the side of the substrate on which elements are mounted, namely, only the one side of the substrate is encapsulated with a resin composition by molding. Furthermore, on the side of the substrate opposite to the side on which the semiconductor elements are mounted, solder balls are two-dimensionally aligned and bond the substrate to a circuit substrate on which semiconductor devices are mounted. Moreover, as a substrate on which elements are mounted, there is proposed a structure which uses a metal substrate such as a lead frame in addition to the above organic circuit substrates.
These area mounting type semiconductor apparatuses have a structure of one-side encapsulation type according to which only the side of a substrate on which elements are mounted is encapsulated with a resin composition and the side on which solder balls are provided is not encapsulated. Very rarely, in the case of a metal substrate such as a lead frame, an encapsulation resin layer of several ten μm may also be present on the side on which solder balls are present, but an encapsulation resin layer of several hundred μm to several mm is formed on the side on which elements are mounted, and, therefore, this is substantially a one-side encapsulation type. Accordingly, warpages are apt to occur in these semiconductor apparatuses just after molding owing to mismatching in thermal expansion or thermal shrinkage between the organic substrate or metal substrate and the cured resin composition or owing to influence of curing shrinkage during molding and curing of the resin composition.
On the other hand, generation of heat from the semiconductor device steadily increases, and the necessity to dissipate the heat generated from the semiconductor device to the outside of the package through the epoxy resin composition for encapsulation of semiconductors has recently become very important. Hitherto, in the structure of area mounting type semiconductor apparatus, increase of the number of pins of external terminals and miniaturization of package are easy because of possibility of area mounting, and, hence, application of semiconductor devices which generate a large quantity of heat is promoted, and notice is given to dissipation of heat to the outside of the package (PKG). Particularly, in order to promote heat dissipation from the epoxy resin composition to the outside, metal plates which are high in heat dissipation are attached to the package, but there is the limit in promotion of the heat dissipation unless the heat dissipation of the epoxy resin composition for semiconductor encapsulation per se is promoted, and importance of promotion of heat dissipation of the epoxy resin composition is particularly noticed.
However, hitherto, epoxy resins for encapsulation high in thermal conductivity have been developed utilizing alumina and the like (JP-B-7-47682, pages 1-6 and Japanese Patent No. 2874089, pages 1-8), but when they are applied to structures of area mounting type semiconductor apparatuses, there are problems in moldability, especially, bad flash characteristics and leakage of flashes onto the substrate. Furthermore, because of the high modulus of elasticity, warpage occurs in the package and temperature cycle properties are inferior, and hence development of new epoxy resins for encapsulation having high thermal conductivity is of urgent necessity for area mounting type semiconductors.
The present invention provides an epoxy resin composition for semiconductor encapsulation in area mounting type semiconductor apparatuses which is excellent in its molding operability, especially, satisfactory in flash characteristics, and furthermore shows substantially no warpage during soldering treatment after molding and has high resistance to temperature cycle, high soldering crack resistance and high thermal conductivity, and further provides a semiconductor apparatus obtained using the above epoxy resin composition.